NetKVM: fix possible 'Nbl' NULL pointer usage (CA)
NetKVM: fix possible 'Nbl' NULL pointer usage (CA)

Protect NdisSendNetBufferLists from passing Nbl == NULL.

Signed-off-by: Viktor Prutyanov <5d18a6677f95b542ec3825271114e4de0d4487e1@phystech.edu>

vrozenfe/kvm-guest-drivers-windows,vrozenfe/kvm-guest-drivers-windows,vrozenfe/kvm-guest-drivers-windows,YanVugenfirer/kvm-guest-drivers-windows,daynix/kvm-guest-drivers-windows,virtio-win/kvm-guest-drivers-windows,virtio-win/kvm-guest-drivers-windows,virtio-win/kvm-guest-drivers-windows,YanVugenfirer/kvm-guest-drivers-windows,virtio-win/kvm-guest-drivers-windows,virtio-win/kvm-guest-drivers-windows,daynix/kvm-guest-drivers-windows,daynix/kvm-guest-drivers-windows,YanVugenfirer/kvm-guest-drivers-windows,vrozenfe/kvm-guest-drivers-windows,daynix/kvm-guest-drivers-windows,YanVugenfirer/kvm-guest-drivers-windows,vrozenfe/kvm-guest-drivers-windows,daynix/kvm-guest-drivers-windows,YanVugenfirer/kvm-guest-drivers-windows